Oscillatory penetration of near-fields in plasmonic excitation at metal-dielectric interfaces.

Lee SC, Kang JH, Park QH, Krishna S, Brueck SR - Sci Rep (2016)

Bottom Line:
This unusual field penetration is explained by the interference between these contributions, and is experimentally confirmed through an aperture which is engineered with four arms stretched out from a simple circle to manipulate a specific plasmonic excitation available in the metal film.A numerical simulation quantitatively supports the experiment.This fundamental characteristic will impact plasmonics with the near-fields designed by aperture engineering for practical applications.

Affiliation: Center for High Technology Materials and Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM 87106, USA.

ABSTRACTThe electric field immediately below an illuminated metal-film that is perforated with a hole array on a dielectric consists of direct transmission and scattering of the incident light through the holes and evanescent near-field from plasmonic excitations. Depending on the size and shape of the hole apertures, it exhibits an oscillatory decay in the propagation direction. This unusual field penetration is explained by the interference between these contributions, and is experimentally confirmed through an aperture which is engineered with four arms stretched out from a simple circle to manipulate a specific plasmonic excitation available in the metal film. A numerical simulation quantitatively supports the experiment. This fundamental characteristic will impact plasmonics with the near-fields designed by aperture engineering for practical applications.

f1: A schematic illustration of a device structure consisting of an MPC and a QDIP.The device structure on the left with a 3 × 3 circular hole MPC at the top is used for the simulation. The absorber on the right shows the detailed structure used in the experiment with a magnification of a single QD stack. In the simulation, these 15 QD stacks were regarded as a single layer with averaged material properties for convenience.

Mentions:
We consider a 100-nm thick gold MPC with a 2-dimensional (2D) square array of circular apertures of diameter d, and evaluate the near-fields by a finite-difference time-domain (FDTD) method. For comparison with experiment, the MPC simulation includes an InAs QDIP. Figure 1 is a schematic illustration of the device structure used in both the simulation and the experiment that is aligned to the z-axis. It consists of an MPC and a 930 nm-thick absorber (15 stacks of InAs QD layers) sandwiched by a 200 nm-thick and a 2 μm-thick n+-GaAs layer (for top and bottom ohmic contacts) on a semi-infinite undoped GaAs substrate (see Methods for detailed structure). In (1), nD ~ 3.3 of the GaAs-based QDIP employed in this work. By setting p = 3.1 μm, the wavelengths of SR1 and SR2, λSR1 (=λ0,1) and λSR2 (=λ1,1), become ~10 μm and 7 μm from (1) respectively. At these wavelengths, the Au skin depth (<30 nm) is considerably smaller than the 100 nm film-thickness and direct transmission through the MPC is negligible14.

f1: A schematic illustration of a device structure consisting of an MPC and a QDIP.The device structure on the left with a 3 × 3 circular hole MPC at the top is used for the simulation. The absorber on the right shows the detailed structure used in the experiment with a magnification of a single QD stack. In the simulation, these 15 QD stacks were regarded as a single layer with averaged material properties for convenience.

Mentions:
We consider a 100-nm thick gold MPC with a 2-dimensional (2D) square array of circular apertures of diameter d, and evaluate the near-fields by a finite-difference time-domain (FDTD) method. For comparison with experiment, the MPC simulation includes an InAs QDIP. Figure 1 is a schematic illustration of the device structure used in both the simulation and the experiment that is aligned to the z-axis. It consists of an MPC and a 930 nm-thick absorber (15 stacks of InAs QD layers) sandwiched by a 200 nm-thick and a 2 μm-thick n+-GaAs layer (for top and bottom ohmic contacts) on a semi-infinite undoped GaAs substrate (see Methods for detailed structure). In (1), nD ~ 3.3 of the GaAs-based QDIP employed in this work. By setting p = 3.1 μm, the wavelengths of SR1 and SR2, λSR1 (=λ0,1) and λSR2 (=λ1,1), become ~10 μm and 7 μm from (1) respectively. At these wavelengths, the Au skin depth (<30 nm) is considerably smaller than the 100 nm film-thickness and direct transmission through the MPC is negligible14.

Bottom Line:
This unusual field penetration is explained by the interference between these contributions, and is experimentally confirmed through an aperture which is engineered with four arms stretched out from a simple circle to manipulate a specific plasmonic excitation available in the metal film.A numerical simulation quantitatively supports the experiment.This fundamental characteristic will impact plasmonics with the near-fields designed by aperture engineering for practical applications.

Affiliation:
Center for High Technology Materials and Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM 87106, USA.

ABSTRACTThe electric field immediately below an illuminated metal-film that is perforated with a hole array on a dielectric consists of direct transmission and scattering of the incident light through the holes and evanescent near-field from plasmonic excitations. Depending on the size and shape of the hole apertures, it exhibits an oscillatory decay in the propagation direction. This unusual field penetration is explained by the interference between these contributions, and is experimentally confirmed through an aperture which is engineered with four arms stretched out from a simple circle to manipulate a specific plasmonic excitation available in the metal film. A numerical simulation quantitatively supports the experiment. This fundamental characteristic will impact plasmonics with the near-fields designed by aperture engineering for practical applications.